Field of the Invention
The invention relates to a process for the preparation of lactams which are N-substituted by aliphatic radicals by reaction of appropriately substituted lactam N-carboxylates or lactim O-carboxylates at elevated temperature and if appropriate in the presence of catalysts. The necessary lactam N-carboxylates or lactim O-carboxylates can be prepared in situ from lactams which are unsubstituted on the nitrogen and aliphatic carbonates or pyrocarbonates and are immediately further converted to the N-substituted lactams without intermediate isolation.
Lactams substituted on the N atom by aliphatic groups, such as N-methyl-pyrrolidone (NMP) or N-methyl-caprolactam (NMC), are important industrial aprotic solvents, especially for extractions and extractive distillations; they can also be employed as basic compounds for the deacidification of natural gas or industrial gases (Chem. Techn [Leipzig], 33 (4) (1981), 193-196).